Relaxation oscillation generator



ii .a u y 3 J n J DDLDDI 111111 Filed Jung 2 1937 M GEIGER RELAXATION,OS C ILLATION GENERATOR INVENTOR M. 2/6512 BY Y ATTORNEY May 23, 1939.

ZEkOl/N t/ Y Emu/v5) PatentedMay 23, .1939

PATENT orrics RELAXATION OSCILLATION GENERATOR Max Geiger, Berlin,Germany, assignor to. we

funken Geoeilschatt tiir Drahtiose Telegraphie m. b. IL, Berlin,Germany, a corporation oiGer- Application June 2. 1937, Serial No.145,014

In Germany June 8, 1936 i a Claim. (Cl. ate-cs) A multivibrator is knownto be a relaxation oscillation generator containing two discharge paths,acting substantially in an alternative fashion, and in which the currentpassing through each of the two discharge paths is interrupted whenevercurrent appears in the other discharge path. Such relaxation oscillationgenerators have a resistance-capacity member for each discharge pathconsisting of a condenser and a resistor connected in series, the oneside of said resistance-capacity member being always connectedrespectively to the other discharge I path. The other side 01' theresistance-capacity member was hitherto connected to the cathode of therespective discharge path. Such relaxation oscillation generators havethe disadvantage that the frequency of the relaxation oscillations whichthey produce is influenced to a comparatively high degree by theso-called disturbance level, i. e.- by the disturbances of nearbycircuits inductively, or .capacitively transmitted in the relaxationoscillation circuit.

In order to avoid this disadvantage the resistance-capacity member ofeach discharge path instead of being connected to the cathode is placedin accordance with the inventioh at a point of a potential that is.pomtive 'relative to the cathode. The sensitivity to disturbances of therelaxation oscillationgenerator can in this way be decreasedto a greatextent.

.The features of my invention are shown in the accompanying drawing inwhich:

Fig. 1 shows a circuit diagram oi my improved multivibrator.

.- Fig. 2 shows a curve of the grid potential of Fig. 6 shows a curve ofthe grid voltage variation in accordance with my invention. Beforeelucidating the functioning of the circuit arranged in accordance withthe invention,

byway 01 an example of construction, there will now be explained byreference to Figure 1 relating to a multivibrator in the known circuit.the

production of relaxation oscillations under the influence ofresistance-capacity members connected to the cathodes oiitheappertaining dis- 1 charge paths, and the sensitivityto disturbanceshall be briefly explained.

i m Figure 1, items in ,and u designate a";

common battery. 20.

.rent. Assuming that the dependence of the rec- 'tifier current J. onthe voltage U takesthe .amplii ier tubes whose plate circuits containthe resistors i2 and it, while the cathodes thereoi' are connected toeach other. A condenser is inserted between the anode of tube II and thegrid of tube It, and a resistor is placed between this 5 for the tube Hand which consists of a condenser I i6 and a resistor il. Furthermore,it is assumed that between the control gridsot the two tubes and thecathodes a rectifier II and I9 respectively be placed together with'abias voltage source represented in Figure 1 by a part of the In thecircuit shown in Figure 1, assume that the resistances l5 and I] areconnected directly between the control electrodes and the cathodes oiltubes iii and II respectively; that is, the conductor ii is connectedtoground potential. Assume further that the tube Ii conducts current, andthat the condenser it has a high charge in the sense of the signsindicated. The grid po-' tential oi the tube" lies then far below thelower bend oi the plate current-grid voltage characteristic. In Figure2, showing the grid potential of tube iii as function of the time, ahighly negative grid potential is thus present at this moment asindicated at the point h. The 3 grid potential is traced in Figure 2 inthe direction downwards from the zero line. The line K corresponds withthe value oi the potential at which current begins to flow inthe tubeIll, 1. e. corresponding to the lower bend of the curve represented inFigure 3 and showing the dependence of the plate' current i. on the gridvoltage a The line G correspondsto the grid potential at which therectiflers II, I! begin to carry curcourse shownin Figure 4, thevertical distance of the line G from the zero line corresponds to thevoltage of the tap point P 01' the battery 20 with respect to ground.Beginning with the moment t1 the condenser M will be discharged acrossthe resistor I! in accordance with an e-function, whose time constant isdetermined by the capacity of the condenser II, and by the value 0! theresistor ll, whereby the grid potential of the tube l0 moves towards thezero value. This e-functi'on is represented in Figure 2 by the curve Awhose later part is shown in dotted line.

This curve approaches the zero line as an asymptote. 4 In theintersection point oi the curve A with the straight line Kthe tube Illbegins to conduct current whereby its plate potential decreases owing tothe potential drop produced through the resistor 12. Hence, the gridpotential of thetube ll decreases and likewise the plate current of thistube, so that the voltage drop through the resistor l3 will be reducedwhereupon the plate potential of the tube H increases. This entails afurther potential increase at the grid of tube Iii, so that the platecurrent thereof increases still further, and the plate current of thetube ll drops still further.

This relationship of the plate current of each tube to the platepotential of the other respective tube as determined by the circuit,leads to a complete interruption of the plate current in tube ,il whilethat of tube Ill increases until the grid of tube it! has only such alow negative po tential relative to the cathode of this tube that therectifier it permits the passage of current. From this moment, asindicated at the point is in Figure 2, the grid potential of the tubeit, and also its plate current, remain at first constant. The condenserit which was charged during the time t1, s will now be dischargedbeginning at themoment represented at point t: in accordance with ane-function whose course likewise approaches the zero line as anasymptote as in the case of the curve A in Figure 2. This is shown inFigure 5 in which the grid potential of the tube II is traced from thezero line downwards as function of the time. Durin the time t1, if: thisgrid potential is constant since during this time the rectifier i9permitted the passing of current. At the moment in the grid potentialbecomes negative quickly because of the rapid current increase in thetube It), and, from the moment is on, the said discharge of thecondenser l6 takes place in accordance with the e-function B. At themoment that the curve B passes through the line K, which has the samesignificance as that in Figure 2, current begins to flow in the tube llcausing an interruption of the plate current in the tube Ill for thesame reason as explained in connection with Figure 2. The grid potentialof the tube II is then again constant from the moment is on, because-0fthe passage of current through the rectifier l9, and the grid potentialof the tube Ill again takes its course in accordance with an e-function.

The influence of disturbance potentials at the grids of the tubes can beeasily recognized by an inspection'of the Figures 2 and 5. Assuming thatthis disturbance potential consists of short, irregularly appearingvoltage impulses oi i'or instance 0.1 volt,'the setting in of adischarge current in one of the two tubes, and hence the interruption oftheplate current in the other tube, can take place when'the curve A or Bis still apart from the line K by 0.1 volt. Therefore, in Figures 2 and5, there'is shown at a distance of 0.1 volt above the curves A and B,second curves A, B, whose intersection points with the lines K determinethe earliest moment in which the relaxation oi the multivibrator canoccur under the influence of the disturbance potentials. The disturbancepotential. can thus have the effect that the time period t1, ta or t isa transmitter.

4 In; accordance with the invention therefore, the resistors I, I1 arenot to be connected to the cathode of the tubes I0, H, but to a point ofthe voltage source 20 that is positive relative to the cathodes of thetubes. This is indicated in Figure 1 by the line 2|.

This modification of the circuit has the effect that the curves A and Bno longer approach the zero line in Figures 2 and 5 as asymptote, butinstead approach a horizontal line Z lying above this zero line.v Thisis shown in Figure 6 for the tube I Ii. The zero line in Figure 6corresponds to the cathodepotential of the tube l0, and the. asymptoteof the grid voltage course A", designated by Z, lies above the zero lineto the extent in which the connection point of the line 21 which isdotted in Figure 1 is apart from the cathode potential. Figure 6 showsthat the curve A" intersects the line K at a steeper angle than in thecase of the curve A in Figure 2. Accordingly, when assuming adisturbance potential having the same value as was presupposed the timet tz-and t2, t2 is to be the same, is to be chosen .difierently from thecasein which the resistance-capacity members have cathode potential.

Various modifications may be made in my invention without departing fromthe spirit and scope thereof and I desire, therefore, that any suchlimitations shall be placed thereon as are imposed by the prior art andare set forth in the appended claims.

I claim as my invention:

x 1. An oscillator for producing a saw-tooth wave -form comprising apair of electron discharge devices each of which'includes a cathode, acontrolelectrode, and an anode, means including anode resistances formaintaining said anodes positive with respect to said cathodes, meansincluding electron storage devices for connecting the anode of eachdischarge device to the control electrode of the other discharge device,a pair of resistances, means 'for connecting one end or each resistanceto said control electrodes, and means for maintaining the other ends ofsaid pair 01 resistances positive with respect to said cathodes andnegative with respect to said anodes.

2. An oscillator for producing a saw-tooth wave form, comprising awpairof electron 'discharge devices each of which includes a cathode, acontrol electrode, and an anode, means including anode resistances formaintaining said anodes positive with respect to said cathodes, meansincluding electron storage devices for connecting the anode of eachdischarge device to the control electrodes of the other dischargedevice, a pair oi resistances, means for connecting one end of eachresistance to said control electrodes, means for maintaining the otherends of said pair of resistances positive with respect to said cathodesand negative with respect to said anodes, a pairoi asymmetric units, andmeans I for connecting saidunits to said control electrodes and to asource of potential negative with respect to said cathodes.

3. An oscillator for producing a saw-tooth wave form comprising a pairor electron dischargedeviceseach of which includes a cathode, a] controlelectrode, and an anode, means infcluding anode resistances formaintaining said anodes positive with respect to said cathodes. meansincluding electron storage devices for connecting the anode of eachdischarge device to the control electrode of the other discharge device,and means including a pair of resistances of potential positive withrespect" to said cathodes. I

4; An oscillator for producing a saw-tooth wave form comprising a pairof electron dis- 1 charge devices each of 'which includes a cathode, acontrol electrode, and an anode, means including anode resistances formaintaining said of potential positive with respect to said cathodes,and means including a pair of asymmetric units for connecting saidcontrol electrodes to a source of potential negative with respect to macathodes.

5.An. oscillating circuit for producing a sawm connecting said controlelectrodes to a source anodes positive with respect to said cathodes,

tooth wave form comprising a pair of electron discharge tubes eachincluding an anode, a control electrode, and a cathode, means includingapair ofresistances for connecting said anodes to a source of potentialpositive with respect to said cathode, a condenser connected between theanode of each tube and the control electrode of the other tube, aresistance connected to the control electrode of each tube, and meansfor connecting the other end of the control electrode resistances to apotential positive with respect to said cathodes.

, 6. An oscillating circuit for producing a sawtooth wave formcomprising a pair of electron discharge tubes each including an anode, acontrol electrode, and a cathode, means including apair of resistancesfor connecting said anodes to a source of potential positive withrespect to said cathode, a condenser connected between the anode of eachtube and the control electrode of the other tube, a resistance'connectedto the control electrode oteach tube, means for connecting the

